Master Degree / Yüksek Lisans Tezleri
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Master Thesis Preparation of Molecularly Imprinted Polymers for the Solid Phase Extraction of Pyridoxal 5'-phosphate Prior To Hplc Determination(Izmir Institute of Technology, 2022) Özyurt, Ömer; Eroğlu, Ahmet EminThree different sorbent materials were prepared for solid phase extraction of pyridoxal phosphate (PLP), namely, carbon sphere based molecularly imprinted chitosan polymer (MICP), magnetite based molecularly imprinted chitosan polymer (MMICP) and silica (sol-gel) based molecularly imprinted polymer (IMIP). The sorbents were characterized by FT-IR, SEM, EDX, XRD, and TGA. The characterization data have shown that, the sorbents were relatively homogeneous, had very fast sorption kinetics and quantitative sorption over a wide range of analyte concentrations (1.0-100.0 mg/L). All the sorbents were found to be selective to PLP in presence of similar compounds; namely, pyridoxamine, nicotinic acid (vitamin B3), pyridoxal and 4-pyridoxic acid. Sorption parameters for each sorbent were optimized. The optimum sorbent amount for 10.0 mL sample volume was found to be 5.0 mg for MICP and 10.0 mg for both MMICP and IMIP. A shaking duration of 30 min was employed in sorption experiments. Among the potential eluents, acetic acid solution (2%, v/v) has shown the best desorption performance for all three sorbents. Method validation was investigated via spike recovery tests on water (ultra-pure, bottled and tap) and artificial serum samples. The recoveries obtained with water samples were greater than 96%, 92%, and 91% for MICP, MMICP, and IMIP, respectively. These results show the potential application of the methodologies for samples with relatively simple matrix. High recoveries (greater than 80%) were also obtained with artificial serum samples, whereas the use of matrix-matched calibration or internal standardization is suggested together with protein precipitation for biological samples with high protein content.Master Thesis Solid Phase Extraction of Ascorbic Acid With Zero-Valent Iron Nanoparticles(01. Izmir Institute of Technology, 2021) Yıldız, Cemre; Eroğlu, Ahmet EminVitamin C (ascorbic acid, AA) is an essential food for humans. It is a watersoluble vitamin found naturally in some foods. With its reducing and chelating capabilities, ascorbic acid is the most effective enhancer of non-heme iron absorption. Sensitive and selective determination of ascorbic acid is necessary in a variety of samples. In this study, molecularly imprinted polymers (MIPs) were synthesized by polymerization strategies and magnetic imprinting technology. Four different synthesis routes were employed, and the magnetic property of the MIPs was brought in with the use of nanosized zero-valent iron (nZVI). Nano zero-valent iron was synthesized using NaBH4 reduction of aqueous Fe+2 ions and used in the solid phase extraction of ascorbic acid prior to HPLC determination. The sorption percentage of the sorbent increased with icreasing pH and reached its maximum level between pH 6.0 and 8.0. Iron oxidation occurs very slowly if the pH is less than 6.0. As a result, when pH 8.0 and higher were tested, there was no effect. The precipitation of iron at pH 8.0 and above could have caused this. The pH level was fixed to 6.0, and the rest of the studies were carried out at this level. The optimal sorbent concentration, solvent concentration, and shaking time were determined to be 10.0 mg, 10.0 mL, and 1 hour, respectively. MeOH and MeOH: H2O, 85:15, were used to achieve desorption (pH of the eluent was adjusted to 3.0 using acetic acid). Finally, the characterization of synthesized nanosized zero-valent iron and magnetic MIP/NIP was carried out through the sorption studies and with the use of XRD, SEM and EDX.Master Thesis Preparati̇on of Fe and Fe-Ni Based Molecularly Imprinted Polymer for Solid Phase Extraction of Salicylic Acid(01. Izmir Institute of Technology, 2021) Bildik, Zeynep; Eroğlu, Ahmet EminAspirin is the most preferred pain reliever among the people. Salicylic acid (SA) is the drug active ingredient of aspirin and has an antipyretic, analgesic, and anti-inflammatory properties. It is also used in the treatment of acne, fungus, varicose veins, and calluses. The aim of this project is to prepare Fe and Fe-Ni based molecularly imprinted polymers (MIPs) for solid phase extraction of salicylic acid and then determine it with HPLC-DAD. MIPs were prepared by using methanol as porogen, 4- vinyl pyridine as monomer, ethylene glycol dimethacrylate cross linker and the analyte, salicylic acid, as the template. Fe and Fe-Ni is used to prevent the hydroxyl and carboxyl groups in the structure of salicylic acid from forming hydrogen bonds between themselves. In this study, a magnetic molecular imprinting solid phase extraction (MMISPE) methodology was proposed for determination of salicylic acid to HPLC-DAD analysis. For this goal, critical experimental parameters of MMISPE method were optimized and determined as follows; sorbent amount of 25.0 mg for 10.0 mL of 5.0 mgL-1 working solution, sorption time of 30 min and MeOH: Acetic acid (9:1) as desorption solvent. The proposed method was repeated with same sorbent and MIPs show quantitative sorption in three times. For characterization of MIPs and NIPs, EDX and XRD analysis was done. In XRD diffractogram, the peaks are relatively low intensities indicate that the material is mostly amorphous. Also, Fe and Ni peak cannot observe because of the trace amount of Fe and Ni in the polymer in the EDX graph.Master Thesis Development of Novel Columns for Determination of Various Ss-Blockers by Capillary Electrochromatography(Izmir Institute of Technology, 2018) Gürel, Elif; Eroğlu, Ahmet Eminß-blockers are one group of the most widely used drugs to treat heart failure, high blood pressure and abnormal heart rhythms. The purpose of this study was to develop capillary columns of stationary phases from molecular imprinting and sol-gel methodology for the determination of ß-blockers prior to capillary electrochromatography (CEC) analysis. In the first part of the study, molecularly imprinted organic based polymers (MIPs), silica-based molecularly imprinted polymers (SMIPs) and silica-based sorbents were developed, characterized and utilized for sorption of metoprolol, an example of ß-blockers. The three different types of sorbents were studied as stationary phases of capillary column. Critical parameters on sorption of metoprolol were investigated. In the second part, the subsequent studies were concentrated on the preparation new capillary column for separation and determination of metoprolol for CEC analysis. The performance of three different types of sorbents was compared. Molecularly imprinted organic polymers show higher sorption and selectivity towards metoprolol as compared with the other sorbent types. The preparation of stationary phases of capillary columns with molecular imprinted organic polymers was proposed for determination of metoprolol prior to CEC analysis. After stationary phase optimization studies, an open tubular column was prepared and its performance was examined.Master Thesis Development of Novel Columns for Determination of Various Diuretics by Capillary Electrochromatography(Izmir Institute of Technology, 2018) Yaşar, Cemre; Eroğlu, Ahmet EminDiuretics are active pharmaceutical compounds that are used for the treatment of edema, cirrhosis, hypertension and renal failure. World Anti-Doping Agency has announced diuretics as banned compounds. Because they are used as a masking and doping agent. In this study, target compounds are therapeutically important groups of this active pharmaceuticals; namely thiazides (bendroflumethiazide, chlorothiazide, hydrochlorothiazide). Sol-gel chemistry and molecularly imprinted polymers (MIPs) methodology were offered for preparing the column for capillary electrochromatography (CEC) for determination of thiazides. Modified silica sol-gel (amine and phenyl modified) and MIPs were synthesized through different routes (inorganic and organic form) as filling materials for capillary columns. Materials which were filled into the column were selected by the help of sorption studies prior to CE-DAD analysis. For this purpose, critical experimental parameters of CE-DAD were optimized and determined as follows; background electrolyte type of borate buffer (10mM) and pH of 9.4, voltage of 25 kV, cassette temperature of 30℃. Limit of detection (LOD) were calculated as between 0.20 mg L-1 and 0.30 mg L-1. Limit of quantification (LOQ) was found as between 0.44 mg L-1 and 0.99 mg L-1. Finally, sorbents having best sorption capacity towards the analytes were prepared as a stationary phase of capillary column and analysis was done with CEC-DAD.Master Thesis Solid Phase Extraction of Ibuprofen in Waters With Molecularly Imprinted Polymers Prior To Hplc-Dad Determination(İzmir Institute of Technology, 2016) Ölçer, Yekta Arya; Eroğlu, Ahmet EminEndocrine disrupting compounds (EDCs) attract great attention worldwide due to their undesired effects on human health. Ibuprofen, an example of endocrine disrupters, is a nonsteroidal anti-inflammatory drug (NSAID). In this study, highly selective molecularly imprinted polymers (MIPs) with different morphologies (as monolith and microspherical beads) were synthesized by bulk and precipitation polymerization strategies. MIPs were prepared by using acetonitrile as porogen, methacrylic acid (MAA) as monomer, trimethylolpropane trimethacrylate (TRIM) as crosslinker and the analyte, ibuprofen, as the template. MIPs revealed higher affinity to the template molecule as compared with non-imprinted polymers (NIPs). The MIP prepared by precipitation polymerization was decided to be used as the primary solid phase extraction (SPE) sorbent due to its higher binding capacity towards ibuprofen compared to the MIP prepared by bulk polymerization. Selectivity of MIP to ibuprofen was examined in the presence of structurally related compounds. In this study, a molecular imprinting solid phase extraction (MISPE) methodology was proposed for determination of ibuprofen prior to HPLC-DAD analysis. For this purpose, critical experimental parameters of MISPE method were optimized and determined as follows; solution pH of 8.0, sorbent amount of 25.0 mg for 10.0 mL of 1.0 mgL-1 working solution, sorption time of 30 min and MeOH:H2O (acetic acid, pH 3.0) ratio of 80:20 as desorption solution. The accuracy of the proposed methodology was verified with spike recovery tests for tap and drinking waters and overall recovery was found as 97.4 (± 0.3) for n=3.Master Thesis Preconcentration of Rare Earth Elements (rees) Using Silica Gel Modified With Several Functional Groups(Izmir Institute of Technology, 2007) Ünal, Semira; Eroğlu, Ahmet Emin; Eroğlu, Ahmet EminDetermination of rare earth elements (REEs) in environmental samples can be performed by inductively coupled plasma optical emission spectrometry (ICP-OES) and inductively coupled plasma mass spectrometry (ICP-MS), in addition to other spectrometric and chromatographic methods. Although these plasma-based techniques offer a good quality data for the determination of REEs, an efficient separation/preconcentration technique prior to instrumental measurements may still be required due to low concentrations and the presence of heavy matrix, in order to achieve accurate and reliable results. In this study, silica gel modified with various organic compound containing S and N functional groups was proposed as adsorbent material for preconcentration of REEs in environmental waters before ICP-MS determination. These organic compounds are (3-aminopropyl)trimethoxysilane (APTMS), (3-mercaptopropyl) trimethoxysilane (MPTMS), 2.aminophenol, 2-aminothiophenol, 2-aminobenzothiazole and L-glutamic acid dimethyl ester. It was shown that REEs can be sorbed by only APTMS and MPTMS modified silica gel quantitatively in a broad pH range (pH>3). At high REEs concentration APTMS modified silica gel (silicaamino) worked better than silica gel. Up to 10.0 mg/L, silica-amino have sorbed higher than 80% of the REEs while silica gel could sorb only 30% of them. Among the sorbents investigated silica-amino was chosen for subsequent experiments. Desorption from APTMS modified silica and silica gel was realised with 1.0 M HNO3. Spike recovery tests were performed in various water types including ultra pure water, sea water, tap water and geothermal water and were found to change between 81-110%.Master Thesis Speciation of Chromium in Waters Via Sol-Gel Preconcentration Prior To Atomic Spectrometric Determination(Izmir Institute of Technology, 2007) Kumral, Elif; Eroğlu, Ahmet EminChromium occurs in natural samples in two relatively stable valence states, i.e. in the form of Cr(III) and Cr(VI) species. Their concentration in natural waters is usually very low, in the order of a few .g/L. This low concentration necessitates either the use of very sensitive analytical techniques or the application of suitable preconcentration methods prior to instrumental determination. In the present study, a resin having immobilized mercapto or amino functional groups was prepared by reacting silica gel with 3-mercaptopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, L-glutamic acid dimethyl ester, aminophenol, aminothiophenol and aminobenzothiazol for the preconcentration of Cr(III) and Cr(VI) species in waters prior to their determination by flame atomic absorption spectrometry (FAAS). Characterization of the novel sorbents were performed using scanning electron microscopy (SEM/EDS), thermo gravimetric analysis (TGA) and elemental analysis. Among the sorbents synthesized, amino sol-gel and silica amino have been shown to be efficient in terms of sorption capacity. The applicability of the new sorbents for the preconcentration of Cr(III) and Cr(VI) species in waters was examined by batch method. After pH 4, silica amino could quantitatively sorb both Cr(III) and Cr(VI) whereas amino sol-gel sorbed only Cr(III). Effect of the amount of silica amino and amino sol-gel was examined at the optimum pH. The optimum amount of silica amino for quantitative sorption was found to be 0.1 g for 20.0 mL of 1.0 mg/L Cr(III) and Cr(VI) solutions whereas that of amino sol-gel was 0.05 g for 20.0 mL of 1.0 mg/L for both species. The effect of Cr(III) and Cr(VI) concentrations on amino sol-gel and silica amino were investigated at the initial concentrations of 1.0, 10.0, 25.0 and 50.0 mg/L. Elution was realized with 2.0 M HCl, and the percent recovery values changed between 60 and 80%.Master Thesis Speciation and Preconcentration of Inorganic Antimony and Manganese in Waters Using Microcolumn-Flow Injection System and Determination by Atomic Absorption Spectrometry(Izmir Institute of Technology, 2003) Erdem, Aslı; Eroğlu, Ahmet EminA selective separation/preconcentration method utilizing microcolumn of a chelating resin with -SH functional groups (Duolite GT-73) was proposed for the determination of Sb(III) in waters by segmented flow injection HGAAS. The selectivity of the resin towards Sb(III) and Sb(V) was not dependent on the pH of the solution; Sb(III) was retained by the resin quantitatively in a broad pH and acidity range whereas Sb(V) was not retained at all and could be determined after a pre-reduction step with L-cysteine.Spike recoveries were tested at various concentration levels in different water types and were found to vary between 80-110 %. Accuracy of the proposed methodology was checked by analyzing a standard reference material and a good correlation was found between the determined and the certified values. The method was applied to several bottled drinking water samples for antimony determination. The samples were found to contain no antimony above the permissible level (5 ug/L). The applicability of the microcolumn separation/preconcentration method for flow injection systems was also demonstrated.A similar separation system was proposed for Mn determination in waters. A macroporous resin with no functional groups (Amberlite XAD-7HP) was employed for the speciation of Mn(II) and Mn(VII) and was found to retain Mn(VII) at pH values from 4.0 to 12.0. Mn(II) was retained at a pH of 12.0, possibly due to MnO2 precipitation rather than adsorption by the resin.Master Thesis Preconcentration of Heavy Metals in Environmental Samples by Biosorption and Determination by Atomic Spectrometry(Izmir Institute of Technology, 2007) Şeker, Ayşegül; Eroğlu, Ahmet Emin; Eroğlu, Ahmet EminIn the assessment of environmental quality, one of the priorities must be given to the determination of heavy metals. In the present study, Spirulina platensis, a cyanobacteria (or blue-green alga) was suggested to be used as a biosorbent prior to the atomic spectrometric determination of Pb, Cd and Ni in some environmental samples. For this purpose, the parameters which might be effective on the biosorption were investigated such as pH, time, initial metal ion concentration, biosorbent amount, temperature, kinetics of sorption, repetitive reactivity and ionic competition. According to the sorption kinetics, results obeyed well the pseudo second-order model. Freundlich, Dubinin Radushkevich and Temkin isotherm models were applied in describing the equilibrium partition of the ions. Freundlich isotherm was applied to describe the design of a single-stage batch sorption system. Thermodynamic parameters (.G0, .H0 and .S0) were calculated and the sorption process was found to be largely driven towards the products and it had an endothermic nature. Faster adsorption kinetics was observed for Pb2+ ions in comparison to Cd2+ and Ni2+ ions. Based on kinetic modeling, the apparent activation energy, Ea, was calculated to be 44 kJmol-1, -16 kJmol-1 and 54 kJmol-1 for Pb2+, Cd2+and Ni2+, respectively. The measurements of the repetitive reusability of Spirulina platensis indicated a large capacity towards the three metal ions. Sorption activities in a three metal ion system were studied and at an initial metal concentration of 100.0 mgL-1, % Pb2+ was found to be still high (85%).However, it decreased to less than 20% for Cd2+ and Ni2+ indicating the relative selectivity of the biosorbent towards Pb2+. Finally, the use of Spirulina platensis, in its natural form or after be immobilized onto various matrices (alginate, silicate, carboxymethylcellulose and polysulfone) was planned for the separation of heavy metals from the sample matrix.